1. Field of Invention
The invention relates to a system for determining the return of the photo sensor in a scanner and the method thereof. In particular, the invention relates to a system for determining the return of the photo sensor in a scanner by using a line resistance material and measuring the currents of the two sections defined by the position of the photo sensor.
2. Related Art
The image scanners cannot become popular due to their low resolutions and high prices in the past. In recent years, photo sensors are mass-produced using the mature production technology. Under the competition of all manufacturers, document scanning is accessible to normal users and the scanners have become one device of the personal computer. They are used to convert images of normal pictures, text, and graphs into digital data that can be displayed, edited, stored, and printed in a computer. The huge amount of data in an enterprise can be scanned into files using the scanners and then sent to relevant recipients by E-mail. This avoids the unnecessary use of paper and document transfers. Image scanner manufacturers often give the users software for word recognition, image processing, English-Chinese translation, and faxing. One can thus use the scanner to scan documents and convert the scanned document using the word recognition system into digital codes. This reduces the space for storing documents.
According to their functions and operating methods, the scanner can be divided into the following categories: handheld scanners, flatbed scanners, sheetfed scanners, film scanners, large format scanners, camera scanners, and drum scanners. In particular, the flatbed scanners have more advances in recent years, rendering a more stable scanning quality and lower cost. Moreover, it can be accompanied with an automatic document feeder (ADF), which enables the device to scan a whole set of documents of the same physical size. Therefore, they have become the mainstream on the market.
FIG. 2A shows a top view of the conventional scanner. From the drawing, we can understand the scanning procedure. The photo sensor 120 starts the first base position sensing unit 132 and moves along the direction of the arrow on the scanning platform on which the document 160 is placed until reaching the beginning 225 of the document 160. Afterwards, the document 160 is read into the photo sensor until the rightmost end 230. The photo sensor 120 then returns along the original path back to 132. During the whole scanning process, the photo sensor travels a distance of 2L1. If the rightmost end 230 of the document exceeds the middle line 240, which is midway between the opposite ends of the scanning platform, then some of the scanning time is wasted in non-scanning processes.